Comparison of microbiological and clinical characteristics based on SCC mec typing in patients with community-onset meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia

Abstract

Molecular identification methods based on the staphylococcal cassette chromosome mec (SCC mec) genotype are more reliable than clinical risk factors and demographic data for differentiating community-acquired and healthcare-associated (HCA) meticillin-resistant Staphylococcus aureus (MRSA). However, patients with community-onset (CO) MRSA infections, defined as a culture-positive sample obtained <48 h after admission and from patients with HCA risk factors, have been infrequently studied. This study compared the clinical profiles of different SCC mec genotypes in this group of patients. From 2004 to 2008, the clinical profiles of 122 non-repetitive patients with CO-MRSA infections at a tertiary medical centre in Taiwan were retrospectively recorded and the molecular characteristics of the isolates were examined. The proportion of SCC mec IV/V genotypes increased from 9.5% to 35.3% from 2004 to 2008. There were no differences in demographic data, underlying diseases, invasive procedures or outcomes between the SCC mec II/III and IV/V groups, except that patients with SCC mec II/III genotypes tended to have more HCA risk factors (3.1 vs. 2.4; P = 0.008). Multivariate logistic regression analysis revealed that having at least four HCA risk factors was independently associated with SCC mec II/III. The sensitivity of recovering SCC mec IV/V genotypes from patients with less than four HCA risk factors was 89.3%. This study revealed the emergence of SCC mec IV/V genotypes in CO-MRSA infections. Although the clinical characteristic boundaries between SCC mec II/III and IV/V diminished, having at least four HCA risk factors made the presence of SCC mec IV/V genotypes less likely in patients with CO-MRSA infections.